This invention relates to batteries and especially secondary batteries employing an anode comprising aluminum and a molten, non-aqueous electrolyte containing admixtures of aluminum halide and 1,2,3-trialkylimidazolium halides having the formula TimX: ##STR2## wherein R.sub.1, R.sub.2 and R.sub.3 are independently alkyl groups of 1 to 12 carbons and X is independently halide or mixtures of halides, e.g., chloride and/or bromide. The molar ratio of aluminum hereinafter denoted by Al, to trialkylimidalozium, hereinafter denoted by Tim, in the electrolyte, may be varied over a wide range so as to make the molten electrolyte composition acidic and as such the electrolyte is useful in batteries, especially secondary batteries employing aluminum anodes and a variety of cathodes.
The use of mixtures of 2 moles of anhydrous aluminum halide such as AlCl.sub.3 and 1 mole of a N-alkylpyridinium bromide or chloride as liquid electrolyte for electrodeposition of aluminum on a metal cathode such as iron at about room temperature is disclosed in U.S. Pat. Nos. 2,446,349 and 2,446,350. Also See U.S. Pat. No. 2,446,331. U.S. Pat. No. 4,115,390 (J. Nardi) and U.S. Pat. No. 4,122,245 (J. Nardi, et al.) describe the preparation of 1-alkylpyridinium chloride salts and the use of these salts for the preparation of 2:1 (mole/mole) AlCl.sub.3 :1-alkylpyridinium chloride room-temperature molten salt electrolytes. U.S. Pat. No. 4,122,245 discloses that the 1-alkylpyridinium molten salts are useful as low temperature battery electrolytes and describes a test cell employing aluminum or glassy carbon as the anode and chloranil as the cathode.
U.S. Pat. No. 4,355,086 (Saathoff et al.) discloses that the discharge rate and internal conductivity of a lithium thionyl chloride battery is improved by the addition of a mixture of aluminum chloride and n-butylpyridinium chloride to the cell electrolyte.
The preparation and use of 1,3-dialkylimidazolium chloride salts with aluminum chloride for room-temperature molten salt electrolytes in a battery cell having an aluminum anode and an iron(III)chloride cathode is described by J. S. Wilkes, et al., in the Frank J. Seiler Research Laboratory Technical Report FJSRL-TR-81-0011; ADA 107,989, October, 1981 and Inorg. Chem., 1982, 21, 1263-1264. Wilkes et al. assert that the 1,3-dialkylimidazolium chloroaluminate melts provide an increased liquidus composition range and improved stability to electrochemical reduction compared to the 1-alkylpyridinium chloride-based melts.
R. A. Osteryoung and co-workers at SUNY at Buffalo (J. Electrochem. Soc. (1983), 130 (No. 9) at pages 1965-1967 and 1968-1969) suggest that neutral room-temperature molten salts such as alkylpyridinium chloride or 1,3-dialkylimidazolium chloride-aluminum chloride might be useful for studies of polymer electrodes.
A variety of different batteries, and especially secondary non-aqueous batteries, have been described containing at least one electrode in which the active material is a conjugated polymer such as polyacetylene or polyphenylene. Exemplary disclosures of such batteries are U.S. Pat. No. 4,321,114 to MacDiarmid et al. (1981); European Patent Application No. 36,118 (corresponding to U.S. Ser. No. 220,496); European Patent Application Nos. 58,469 and 76,119, both of Showa Denko K.K.
There is an on-going search for batteries, especially secondary batteries employing useful working electrodes and a room-temperature, molten non-aqueous ionic liquid electrolyte having various physical and chemical properties superior to those of previously reported molten ionic liquid electrolytes, and especially having superior stability to electrochemical oxidation and reduction over a wider liquid composition range.